Interfacial Concentrations of Hydroxytyrosol Derivatives in Fish Oil-in-Water Emulsions and Nanoemulsions and Its Influence on Their Lipid Oxidation: Droplet Size Effects.

Marlene Costa,Carlos Bravo-Díaz,Fátima Paiva-Martins,Luís S Monteiro,Sonia Losada-Barreiro

doi:10.3390/foods9121897

Abstract

Reports on the effect of droplet size on the oxidative stability of emulsions and nanoemulsions are scarce in the literature and frequently contradictory. Here, we have employed a set of hydroxytyrosol (HT) esters of different hydrophobicity and fish oil-in-water emulsified systems containing droplets of different sizes to evaluate the effect of the droplet size, surfactant, (ΦI) and oil (ΦO) volume fractions on their oxidative stability. To quantitatively unravel the observed findings, we employed a well-established pseudophase kinetic model to determine the distribution and interfacial concentrations of the antioxidants (AOs) in the intact emulsions and nanoemulsions. Results show that there is a direct correlation between antioxidant efficiency and the concentration of the AOs in the interfacial region, which is much higher (20–200 fold) than the stoichiometric one. In both emulsified systems, the highest interfacial concentration and the highest antioxidant efficiency was found for hydroxytyrosol octanoate. Results clearly show that the principal parameter controlling the partitioning of antioxidants is the surfactant volume fraction, ΦI, followed by the O/W ratio; meanwhile, the droplet size has no influence on their interfacial concentrations and, therefore, on their antioxidant efficiency. Moreover, no correlation was seen between droplet size and oxidative stability of both emulsions and nanoemulsions.

Highlights

Interest in using fish oils to prepare foods comes from their high content of long chain omega-3 fatty acids present in their triacylglycerols, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) [1]
LEn 1:9 O/W emulsions prepared with ΦI = 0.005 showed droplet sizes above
The more lipophilic esters caused a general increase in the interfacial area values in emulsions loaded with HT derivatives in comparison with the reference

Summary

Introduction

Interest in using fish oils to prepare foods comes from their high content of long chain omega-3 fatty acids present in their triacylglycerols, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) [1]. This is due to the high number of bis-allylic hydrogens bonded in their chemical structure with high susceptibility to homolytic breakdown and consequent formation of radicals [2] This oxidation reaction, leading to the rancidity of the oil and to the production of harmful products, represents, after microbial spoilage, the major cause of food deterioration and rejection by. This oxidation reaction, leading to the rancidity of the oil and to the production of harmful products, represents, after microbial spoilage, the major cause of food deterioration and rejection by both consumers and industry [3,4].

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